1. Field of the Invention
The invention relates to a tensioning clamp for fastening a rail with a centre portion, with at least one torsional portion branching from the centre portion in the lateral direction, with at least one transitional portion adjoining the torsional portion and with at least one holding arm which is connected to the transitional portion and the end portion of which holding arm associated with the free end of the holding arm, viewed in a plan view of the tensioning clamp, is bent to point away from the torsional portion. Tensioning clamps of this type are generally bent in one piece from a spring steel.
The invention also relates to a system for fastening a rail, which has a rail foot, a web standing thereon and a rail head, with a guide plate, a tensioning clamp held on the guide plate and a tensioning means for bracing the tensioning clamp against a base supporting the rail.
2. Description of the Related Art
A tensioning clamp and a system of this type are known from DE 10 2007 046 543 A1. In the known system, a tensioning clamp is used as the spring element for producing the resiliently elastic holding force required to hold down the rail, and, taking into account the length of the carrier plate measured in the longitudinal direction of the rail to be fastened, is designed in such a way that its at least one holding arm can cover maximum spring paths. In this case, the end portion of the holding arm is bent to point away from the torsional portion in such a way that, in the assembly position, it points in the direction of the web of the rail to be fastened. Owing to this measure, on the one hand, the closely limited support region formed on the free tip of the respective end portion, in which the holding arm with its end portion exerts the required holding down force on the rail foot during use, is displaced from the edge of the rail foot in the direction of the rail web of the rail to be fastened. This ensures that the required holding force is also constantly perfectly transmitted by the respective holding arm onto the rail foot when the rail foot, as a consequence of the transverse forces occurring when the rail is traveled over and a lateral support, which is imprecise under some circumstances, on the carrier plate, moves excessively strongly transverse to the longitudinal direction thereof. Moreover, the displacement of the support region in the direction of the rail web brings about a higher resistance against an undesired rotation, so the positionally correct assembly of the tensioning clamp, in particular, is facilitated.
Practical experiences with the system described above show that owing to the bent shaping of the end portions of the holding arms of the tensioning clamp, even when there is a relatively large transverse displacement, the secure hold of the rail is ensured. However, in particular when the rail carries out alternating short transverse movements, when a rail vehicle travels over it, increased abrasive wear occurs in the region of the areas, in which the end portions of the holding arms act on the rail foot of the rail to be fastened. Moreover, the special shaping of the tensioning clamp used in the known system described above proves to be advantageous with regard to a maximum elasticity of the spring. But it is difficult with this shaping, with limited installation space and comparably limited tensioning paths, to exert high spring forces on the rail foot.